This invention relates generally to dimming control systems for lamps, specifically incandescent lamps, and, more particularly, to a dimming control system for traffic control signal lamps.
In recent years, there has been a great deal of effort directed towards developing lighting systems that use less electrical power. A significant amount of energy is wasted by present commercial traffic control lighting systems that are operated at a single power level. The high light output required for visibility during sunrise, sunset and daylight operation greatly exceeds that which is required for visibility during the night hours. Present commercial approaches to conserving traffic light energy by dimming the lamps during hours of darkness have approached the problem by utilizing a chopper network or high current silicon controlled rectifiers in the power path to the lamps. These approaches have certain disadvantages in that the chopper network generates undesirable noise and the silicon controlled rectifier systems are of a high cost and erratic operation.
Therefore, it is a principal object of the present invention to provide a light dimming circuit particularly applicable to traffic lights that overcome these disadvantages and does so in an economical, reliable and flexible manner.